Enhanced channel access mechanisms for wide band operation on unlicensed bands

ABSTRACT

A method for dynamically dividing or consolidating sub-bands in-between Clear Channel Assessment (CCA) status measurements upon detection of a CCA bandwidth adjustment condition is provided. The method includes determining at least a single CCA status for at least a single sub-band during a first period, and detecting a CCA bandwidth adjustment condition for dividing the single sub-band into two or more separate sub-bands, where a combination of the two or more separate sub-bands occupies the same frequency band as the single sub-band. The method also includes determining a separate CCA status for each of the two or more separate sub-bands during a second period. An apparatus for performing this method is also provided.

TECHNICAL FIELD

The present invention relates to a system and method for wirelesscommunications, and, in particular, to a system and method forperforming a Clear Channel Assessment (CCA) on unlicensed wide bands.

BACKGROUND

Unlicensed wireless protocols may attempt to access wireless channelswithout centralized coordination and planning, which may lead tocollisions between different unlicensed transmissions. One technique formitigating such collisions is referred to as Carrier-Sense MultipleAccess/Collision Avoidance (CSMA/CA). CSMA/CA includes a medium sensingstage, also called Clear Channel Assessment (CCA), during which a devicesenses a shared channel to determine a CCA status of a sub-band beforeperforming a transmission.

Modern networks may use CCA on a wideband shared channel, which allows awireless device to transmit or receive data over multiple sub-bands atthe same time in order to increase the bandwidth available to thewireless device. Conventional schemes for wideband medium sensing dividethe spectrum into a static number of sub-bands, and determine a CCAstatus on each sub-band individually. Techniques for improving theefficiency and collision avoidance of wideband medium sensing inunlicensed spectrum shared by coexisting wireless networks are desired.

SUMMARY

Technical advantages are generally achieved by embodiments of thisdisclosure which describe systems and methods for performing an adaptivewideband CCA in accordance with a pattern of interference in unlicensedspectrum.

In accordance with an embodiment, a method for channel access in awireless communication system is provided. In this example, the methodincludes determining at least a single CCA status for at least a singlesub-band during a first period, and detecting a CCA bandwidth adjustmentcondition for dividing the single sub-band into two or more separatesub-bands, where a combination of the two or more separate sub-bandsoccupies the same frequency band as the single sub-band. The method alsoincludes determining a separate CCA status for each of the two or moreseparate sub-bands during a second period. An apparatus for performingthis method is also provided.

In accordance with another embodiment, a method for channel access in awireless communication system is provided. In this example, the methodincludes determining separate CCA statuses for two or more sub-bandsduring a first period, and detecting a CCA bandwidth adjustmentcondition for consolidating the two or more sub-bands into a singlesub-band, where a combination of the two or more sub-bands occupies thesame frequency band as the single sub-band. The method also includesdetermining a single CCA status for the single sub-band during a secondperiod. An apparatus for performing this method is also provided.

In accordance with yet another embodiment, a method for channel accessin a wireless communication system in accordance with channelconfiguration information of coexisting systems is provided. In thisexample, the method includes receiving beacons and/or preambles and/ordiscovery reference signals (DRS) transmitted from different coexistingwireless systems, and calculating priorities for a plurality ofsub-bands in accordance with channel configuration information in thebeacons and/or the preambles received from the different coexistingwireless systems, where sub-bands having higher priorities are lesslikely to be occupied by a data transmission of the different coexistingwireless systems than sub-bands having lower priorities. The method alsoincludes determining one or more CCA statuses for one or more sub-bandsin the plurality of sub-bands in accordance with the priorities for theplurality of sub-bands. An apparatus for performing this method is alsoprovided.

The foregoing has outlined rather broadly the features of an embodimentof the present invention in order that the detailed description of theinvention that follows may be better understood. Additional features andadvantages of embodiments of the invention will be describedhereinafter, which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiments disclosed may be readily utilized as a basisfor modifying or designing other structures or processes for carryingout the same purposes of the present invention. It should also berealized by those skilled in the art that such equivalent constructionsdo not depart from the spirit and scope of the invention as set forth inthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates an embodiment network architecture with interferencein unlicensed spectrum;

FIG. 2 illustrates an embodiment sub-band configuration for a CCA;

FIG. 3 illustrates a flowchart of an embodiment method;

FIG. 4 illustrates a flowchart of another embodiment method;

FIG. 5 illustrates calculation of sub-band priorities in an embodimentmethod;

FIG. 6 illustrates a block diagram of an embodiment processing system;and

FIG. 7 illustrates a block diagram of an embodiment a transceiver.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the embodiments andare not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

It should be understood at the outset that although an illustrativeimplementation of one or more embodiments are provided below, thedisclosed systems and/or methods may be implemented using any number oftechniques, whether currently known or not. The disclosure should in noway be limited to the illustrative implementations, drawings, andtechniques illustrated below, including the exemplary designs andimplementations illustrated and described herein, but may be modifiedwithin the scope of the appended claims along with their full scope ofequivalents.

Unlicensed wireless protocols, such as Wi-Fi (e.g., IEEE 802.11 ac) andLong-Term Evolution (LTE) License Assisted Access (LAA) (e.g., 3^(rd)Generation Partnership Project (3GPP) Technical Specification 36.213),may attempt to access shared channels without centralized coordinationand planning. As a result, unlicensed wireless protocols may besusceptible to collisions between different unlicensed transmissions.One technique for mitigating such collisions is referred to asCarrier-Sense Multiple Access/Collision Avoidance (CSMA/CA). Inparticular, CSMA/CA includes a medium sensing stage, also called ClearChannel Assessment (CCA), during which a device listens, or otherwisesenses, a shared channel to determine a CCA status of a sub-band beforeperforming a transmission. The device should first sense the channel andmake sure the channel stays in an idle CCA status for a period of time,i.e., a backoff period. The backoff period can be interrupted if thedevice detects that the channel changes to a busy CCA status (the energylevel of the noise and interference exceeds a predefined threshold). Thebackoff period may be randomly selected such that devices whichsimultaneously starting medium sensing on the same channel are likely towait different lengths of time which avoids the devices frompersistently detecting busy CCA statuses on the channel.

Modern networks may use CCA techniques on a wideband shared channel,which allows a single wireless device to transmit or receive data overmultiple sub-bands at the same time in order to increase the bandwidthavailable to the wireless device. Conventional schemes for using CSMA/CAon a wideband shared channel divide the spectrum into a static number ofsub-bands, and determine a CCA status on each sub-band individually.

However, coexisting networks or (in some cases) devices in the samenetwork, may use different sub-band configurations, such that a widesub-band that a CCA status is determined over spans a narrower sub-bandthat carries a transmission. This may be problematic for two reasons. Ifthe power level of narrow-band transmission is sufficient to register abusy CCA status over the wide sub-band, then other narrow sub-bandsspanned by the wide sub-band may go unused, thereby reducing resourceutilization efficiency. Alternatively, if the received signal powerlevel of the narrow-band transmission is insufficient to register a busyCCA status on the wide sub-band, then the device performing the CCAmeasurement may proceed to perform a transmission over the widesub-band, and a collision may result. Accordingly, techniques forimproving the efficiency and collision avoidance when CCA is used inconjunction with CA techniques over sub-bands shared by coexistingnetworks are desired.

Aspects of this disclosure provide embodiment techniques thatdynamically divide, or consolidate, sub-bands in-between CCA statusmeasurements upon detection of a CCA bandwidth adjustment condition. Inone embodiment, a CCA bandwidth adjustment condition prompts a wirelessdevice to divide a wider sub-band (e.g., a single 40 megahertz (MHz)sub-band) into two or more narrower sub-bands (e.g., two 20 MHzsub-bands, four 10 MHz sub-bands, etc.) in-between successive CCA statusmeasurements. In another embodiment, a CCA bandwidth adjustmentcondition prompts a wireless device to consolidate two or more narrowersub-bands into a wider sub-band in-between successive CCA statusmeasurements. On one hand, dynamically dividing a wider sub-band intotwo or more narrower sub-bands may increase the accuracy, andgranularity, of CCA status measurements, which may improve collisionavoidance and/or spectral utilization efficiency when a narrow-bandtransmission from another wireless device occurs over one of thenarrower sub-bands. On the other hand, consolidating two or morenarrower sub-bands into a wider sub-band may reduce the number of CCAstatus measurements that the wireless device is required to perform,thereby reducing processing complexity of the CCA scheme when each ofthe two or more narrower sub-bands has an idle CCA status during thesubsequent period.

Various CCA bandwidth adjustment conditions may prompt a wireless deviceto divide a wider sub-band into two or more narrower sub-bands, orotherwise consolidate two or more narrower sub-bands into a widersub-band, in-between successive CCA status measurements. In someinstances, a CCA bandwidth adjustment condition may correspond to CCAstatuses and/or error rates associated with a set of aggregatedsub-bands that are being monitored by a wireless device.

In one example, the wireless device may detect a CCA bandwidthadjustment condition for dividing one of the sub-bands into two or morenarrower sub-bands (which is referred to as a CCA bandwidth adjustmentcondition for dividing sub-bands) when the number of sub-bands in theset of aggregated sub-bands during a reference period, that have an idleCCA status is less than a threshold.

In another example, the wireless device may detect a CCA bandwidthadjustment condition for dividing sub-bands when an error rateassociated with one or more data transmissions over one or moresub-bands in a set of aggregated sub-bands during an initial referenceperiod exceeds a threshold error rate.

The error rate may be determined by a feedback from a receiver, such asa hybrid automatic repeat request (HARQ) acknowledged (ACK), an HARQnot-acknowledged (NACK), an HARQ discontinuous transmission (DTX), or animplicit decoding success indication in up-link (UL) grant downlinkcontrol information (DCI), etc.

In another example, the wireless device may detect a CCA bandwidthadjustment condition for dividing sub-bands when both an error rateassociated with one or more data transmissions over one or moresub-bands in a set of aggregated sub-bands during a reference periodexceeds a threshold error rate, and the number of sub-bands in the setof aggregated sub-bands that have an idle CCA status is less than athreshold number of sub-bands.

In another example, the wireless device may detect a CCA bandwidthadjustment condition for dividing sub-bands when all sub-bands in theset of aggregated sub-bands maintain a busy CCA status for at least athreshold number of periods.

In another example, the wireless device may detect a CCA bandwidthadjustment condition for consolidating two or more narrower sub-bandsinto a single wider sub-band (which is referred to as a CCA bandwidthadjustment condition for consolidating sub-bands) when the number ofsub-bands in the set of aggregated sub-bands, that have an idle CCAstatus is more than a threshold number of sub-bands.

In another example, the wireless device may detect a CCA bandwidthadjustment condition for consolidating sub-bands when an error rateassociated with one or more data transmissions over one or moresub-bands in a set of aggregated sub-bands during an initial referenceperiod is smaller than a threshold error rate.

In another example, the wireless device may detect a CCA bandwidthadjustment condition for consolidating sub-bands when both an error rateassociated with one or more data transmissions over one or moresub-bands in a set of aggregated sub-bands during an initial referenceperiod is smaller than a threshold error rate, and the number ofsub-bands in the set of aggregated sub-bands that have an idle CCAstatus is more than a threshold number of sub-bands.

When there are a set of coexisting wireless systems, upon detecting aCCA bandwidth adjustment condition for either dividing or consolidatingsub-bands, a bandwidth of either each of the two or more separatesub-bands for the dividing condition, or the single sub-band for theconsolidating condition, may correspond to bandwidths used by the set ofcoexisting wireless systems during an initial reference period.

In one example, the bandwidth determined during the next period mayequal the minimum operation bandwidth used by the set of coexistingwireless systems during an initial reference period.

In another example, the bandwidth determined during the next period mayequal an operation bandwidth used by more than a threshold number ofcoexisting wireless systems in the set of coexisting wireless systemsduring an initial reference period.

Other aspects of this disclosure provide embodiment techniques thatcalculate priorities for a plurality of sub-bands when a wireless devicereceives beacons and/or preambles transmitted from different coexistingwireless systems. Sub-bands that have higher priorities are less likelyto be occupied by a data transmission of the different coexistingwireless systems than sub-bands having lower priorities.

The wireless device may determine one or more CCA statuses for one ormore sub-bands in the plurality of sub-bands in accordance with thecalculated priorities. In one example, the wireless device may determineCCA statuses for one subset of sub-bands in the plurality of sub-bands,which have higher priorities, and not determine CCA statuses for anothersubset of sub-bands in the plurality of sub-bands, which have lowerpriorities. In another example, the wireless device may determine a CCAstatus for each of the plurality of sub-bands sequentially in adescending order of the priorities for the plurality of sub-bands.

The above aspects and other inventive aspects are discussed in greaterdetail below.

FIG. 1 illustrates a network 100 for communicating data and potentialsources of interference. The network 100 comprises a base station 110having a coverage area 112, a UE 120, a UE 130, and a backhaul network140. As shown, the base station 110 establishes uplink (dashed line)and/or downlink (dotted line) connections with both the UE 120 and theUE 130, which serve to carry data from the UEs to the base station 110and vice-versa. Data carried over the uplink/downlink connections mayinclude data communicated between the UEs and the base station 110, aswell as data communicated to/from a remote-end (not shown) by way of thebackhaul network 140. A base station 150 and a base station 160 do notcommunicate directly with the UE 120, but base stations 150 and 160 bothoccupy the same shared channel as the network 100. The base station 150uses a same wireless protocol as the network 100 while the base station160 uses a different one. The connections between the UE 120 and thebase station 110 may be interfered by the UE 130, the base station 150or the base station 160. As used herein, the term “base station” refersto any component (or collection of components) configured to providewireless access to a network, such as an enhanced base station (eNB), amacro-cell, a femtocell, a Wi-Fi access point (AP), or other wirelesslyenabled devices. Base stations may provide wireless access in accordancewith one or more wireless communication protocols, e.g., long termevolution (LTE), LTE advanced (LTE-A), LTE License Assisted Access(LAA), High Speed Packet Access (HSPA), Wi-Fi 802.11a/b/g/n/ac, etc. Asused herein, the term “UE” refers to any component (or collection ofcomponents) capable of establishing a wireless connection with a basestation, such as a mobile device, a mobile station (STA), and otherwirelessly enabled devices. In some embodiments, the network 100 maycomprise various other wireless devices, such as relays, low powernodes, etc.

Different sub-band configurations may be used to perform CCA over ashared channel. In one embodiment, a wireless device may select asub-band configuration, from a set of predefined sub-bandconfigurations, for a given shared channel, and then determine a CCAstatus for each sub-band defined by the selected sub-band configurationprior to transmitting data over idle sub-bands of the shared channel.Each of the predefined sub-band configurations may divide the sharedchannel into a different combination of sub-bands. FIG. 2 illustratesdifferent sub-band configurations 210, 220, 230, and 240 for a 160 MHzshared channel. As shown, the sub-band configuration 210 divides theshared channel into eight 20 MHz sub-bands, the sub-band configuration220 divides the shared channel into four 40 MHz sub-bands, the sub-bandconfiguration 230 divides the shared channel into two 80 MHz sub-bands,and the sub-band configuration 240 divides the shared channel into two20 MHz sub-bands, one 40 MHz sub-band, and one 80 MHz sub-band. Althoughsub-bands in each of the respective sub-band configurations 210, 220,230, and 240 are continuous with one another in the frequency domain, itshould be appreciated that some sub-band configurations may includesub-bands that are non-continuous in the frequency domain such that atleast two of the sub-bands are separated by a gap (e.g., a guard band,etc.). In some examples, sub-bands in different sub-band configurationsmay be interleaved with one another in the frequency domain. Otherexamples are also possible.

FIG. 3 illustrates a method 300 for performing the proposed embodimenttechniques in a wireless network. As shown, the method 300 begins withstep 310, where a wireless device is using an initial sub-bandconfiguration during a first period, which divides a shared channel intoa set of aggregated sub-bands. In step 310, the wireless devicedetermines at least a single CCA for at least a single sub-band in theset of aggregated sub-bands. If an idle CCA status is detected on one ormore sub-bands, the method 300 proceeds to step 320 where the wirelessdevice may start data transmission on the one or more sub-bands with anidle CCA status during the first period. The method 300 proceeds to step330, where the wireless device may detect a CCA bandwidth adjustmentcondition, which may indicate a pattern of interference on the sharedchannel has changed. The wireless device may choose to update thesub-band configuration accordingly.

In some instances, the method 300 proceeds to step 340, where the CCAbandwidth adjustment condition prompts the wireless device to divide asingle wider sub-band into two or more separate narrower sub-bands. Acombination of the two or more separate narrower sub-bands occupies thesame frequency band as the single wider sub-band. In some otherinstances, the method 300 proceeds to step 350, where the CCA bandwidthadjustment condition prompts the wireless device to consolidate two ormore separate narrower sub-bands into a single wider sub-band. In bothsteps 340 and 350, upon detection of the CCA bandwidth adjustmentcondition, the wireless device either divides or consolidates sub-bandsand updates the sub-band configuration.

Then the method 300 proceeds to step 360 where the wireless deviceperforms CCA measurements for at least one sub-band according to theupdated sub-band configuration during a second period. In some otherinstances, the CCA bandwidth adjustment condition may not be detected ifthe change of pattern of the interference on the shared channel is notsignificant enough. In this case, the method 300 may proceed from step330 to step 360 directly, and the wireless device performs CCAmeasurements during the second period using the same sub-bandconfiguration as in the first period.

CCA bandwidth adjustment conditions for dividing or consolidatingsub-bands may be based on CCA status measurements corresponding to agiven sub-band, or a given set of aggregated sub-bands, during aprevious CCA period/interval. In one embodiment, a CCA bandwidthadjustment condition for dividing sub-bands may be detected when lessthan a certain number, or less than a certain percentage (e.g., 75%) ofthe sub-bands in a given set of aggregated sub-bands have an idle CCAstatus. For example, the wireless device is currently using the sub-bandconfiguration 220 in FIG. 2. If a previous CCA status measurement showsthat sub-bands 1 and 4 are idle while sub-bands 2 and 3 are busy, thenthe percentage of idle status is 50% which is less than the 75%threshold. Such measurement results may indicate that the interferenceon the shared channel is more severe than previously expected. In thiscase, the wireless device may choose to divide each 40 MHz sub-band intotwo 20 MHz sub-bands so that the sub-band configuration 210 in FIG. 2will be used during the next CCA status measurement. The next CCA statusmeasurement will be performed with a finer granularity, especially forsub-bands 3-6 in the sub-band configuration 210. In another embodiment,a CCA bandwidth adjustment condition for consolidating sub-bands may bedetected when more than a certain number, or more than a certainpercentage of the sub-bands in the given set of aggregated sub-bandshave an idle CCA status. In the above example where the sub-bandconfiguration 220 is used during the previous CCA status measurement, ifthree out of four sub-bands obtain an idle status (the 75% threshold isreached), then the wireless device may choose to consolidate sub-bands 1and 2 into one sub-band, and consolidate sub-bands 3 and 4 into anothersub-band. As a result, the sub-band configuration 230 in FIG. 2 will beused during the next CCA status measurement, which may reduce theprocessing complexity of the measurement.

In an embodiment, the wireless device may not perform dividing orconsolidating on some sub-bands in the set of aggregated sub-bands, andmay do so on some other sub-bands in the set of aggregated sub-bands,even on only one specific sub-band for the dividing case.

In an embodiment, if a CCA bandwidth adjustment condition forconsolidating sub-bands is detected consecutively for several times, thewireless device may choose to consolidate sub-bands every time tilleventually all the aggregated sub-bands are combined to one if thesub-band configuration allows so.

In an embodiment, the CCA bandwidth adjustment condition is detected ifthe wireless device performs consecutive CCA status measurements for athreshold number of times and each time the CCA measurement resultssatisfy a predefined requirement. In this case, the wireless device maynot perform consolidating until the threshold number is reached. In oneexample, the CCA bandwidth adjustment condition is detected if thewireless device performs three consecutive CCA status measurements andevery time all sub-bands have an idle status. In another example, oncethe threshold number is reached, the wireless device may consolidate allthe aggregated sub-bands into one single sub-band.

As shown in step 320 in FIG. 3, during an initial reference period thewireless device may transmit data on one or more sub-bands with an idleCCA status. The CCA bandwidth adjustment condition may correspond to anerror rate of one or more data transmissions over such sub-bands. Theerror rate of the one or more initial data transmissions may bedetermined by a feedback from a receiver of the transmissions. Forinstances, in 3GPP protocols, the receiver may provide feedbacks throughan HARQ ACK, an HARQ NACK, an HARQ DTX, or an implicit decoding successindication in UL grant DCI. Different types of feedbacks in otherwireless protocols are also possible. In one embodiment, when the errorrate associated with the one or more data transmissions over one or moresub-bands in a set of aggregated sub-bands during the initial referenceperiod exceeds a threshold error rate, a CCA bandwidth adjustmentcondition is detected, which prompts the wireless device to divide atleast one wider sub-band in the set of aggregated sub-bands into two ormore narrower sub-bands. In another embodiment, when the error rateassociated with the one or more data transmissions over one or moresub-bands in the set of aggregated sub-bands during the initialreference period is smaller than the threshold error rate, another CCAbandwidth adjustment condition is detected, which prompts the wirelessdevice to consolidate two or more narrower sub-bands in the set ofaggregated sub-bands into a wider sub-band. In another embodiment, thewireless device may perform dividing or consolidating only on sub-bandsthat correspond to the initial data transmissions.

The CCA bandwidth adjustment condition may correspond to a combinationof the error rate of the one or more data transmissions over the one ormore sub-bands in the set of aggregated sub-bands, and the number ofsub-bands in the set of aggregated sub-bands that have an idle CCAstatus. In an embodiment, the CCA bandwidth adjustment condition fordividing sub-bands is detected when both the error rate of the one ormore data transmissions exceeds a threshold error rate, and the numberof sub-bands in the set of aggregated sub-bands having an idle CCAstatus is less than a threshold number of sub-bands. The wireless devicemay divide every sub-band in the set of aggregated sub-bands, and choosean available sub-band configuration with the largest number ofsub-bands. In another embodiment, the CCA bandwidth adjustment conditionfor consolidating sub-bands is detected when both the error rate of theone or more data transmissions is smaller than another threshold errorrate, and the number of sub-bands in the set of aggregated sub-bandshaving an idle CCA status exceeds another threshold number of sub-bands.The wireless device may consolidate all the aggregated sub-bands intoone sub-band if the sub-band configuration allows so.

It should be appreciated that the reference period during which a CCA isperformed may or may not be the same as the one during which an errorrate of initial data transmissions is measured. In one example, both theCCA and the error rate measurement are performed on the first slot orsub-frame in the Maximum Channel Occupancy Time (MCOT). In anotherexample, the CCA occurs on the first slot of the MCOT while the errorrate is measured for all transmissions during the whole MCOT.

The CCA bandwidth adjustment condition may also be determined based onthe channel configuration information of coexisting wireless systems.Some unlicensed wireless protocols broadcast information about thefrequency bands they operate on. For example, a Wi-Fi AP transmits abeacon frame (or a preamble if later versions of Wi-Fi protocols aresupported) periodically, in order to announce the existence of this APand some configuration parameters such as the service set identifier(SSID), channels and capabilities. As for LAA and enhance LAA (eLAA) LTEprotocols, the broadcast information carried by a physical broadcastchannel (PBCH) or a physical downlink control channel (PDCCH) indicatesthe carrier frequencies and how the resources are allocated. If thewireless device has the ability to receive and decode these broadcastmessages from surrounding coexisting wireless systems, it may adjust thesub-band configuration and perform CCA accordingly. In an embodiment,the wireless device may determine the minimum operation bandwidth thatthe coexisting wireless systems have been using for a predefinedreference period (e.g. 100 milliseconds), and then choose this minimumoperation bandwidth as the bandwidth of the CCA sub-bands for the nextperiod. In another embodiment, the wireless device may determine that athreshold number of coexisting wireless systems have been usingsub-bands with bandwidths larger than an operation bandwidth for aprevious period of time. Then the wireless device may choose thisoperation bandwidth as the bandwidth of the CCA sub-bands for the nextperiod.

FIG. 4 illustrates a method 400 for performing an embodiment techniqueto calculate sub-band priorities in a wireless network. In someembodiments, based on the channel configuration information ofcoexisting wireless systems, the wireless device may evaluate whichsub-band within the shared channel is less likely to be occupied by adata transmission of the coexisting wireless systems. The less likelythese sub-bands are occupied, the more likely they are in an idle CCAstatus and are ready to be accessed by the wireless device; hence thewireless device may assign higher priorities to these sub-bands. Asshown in FIG. 4, the method 400 begins with step 410, where a wirelessdevice receives beacons and/or preambles transmitted from differentcoexisting wireless systems, which may include channel configurationinformation of the coexisting wireless systems. The wireless device maydecode the channel configuration information and use that to evaluate aplurality of sub-bands in the shared spectrum.

In step 420, the wireless device calculates priorities for the pluralityof sub-bands in accordance with channel configuration information in thebeacons and/or the preambles received from the different coexistingwireless systems. FIG. 5 illustrates how the priorities are calculatedin an environment of three coexisting Wi-Fi APs. In this example, eachWi-Fi AP can operate on three types of channels—a primary 20 MHz (P20)channel, a secondary 20 MHz (S20) channel, and a secondary 40 MHz (S40)channel.

A Wi-Fi AP may look for a wider frequency band for data transmission. Inaccordance with IEEE 802.11n, the AP will first assess its P20 channel.If the P20 channel is clear or idle, the AP will assess the adjacent S20channel. If the S20 channel is busy, the AP uses only P20 for a 20 MHztransmission. If the S20 is clear, the AP uses both P20 and S20 for a 40MHz transmission. Then the AP will assess the S40 channel adjacent tothe combination of P20 and S20. If the S40 channel is clear, the AP usesall three channels for an 80 MHz transmission. In some Wi-Fi protocols(e.g., IEEE 802.11ac) a secondary 80 MHz (S80) channel may be furtherassessed for a 160 MHz transmission. In some other emerging Wi-Fiprotocols (e.g., IEEE 802.11ay), the primary and secondary channels maynot be adjacent to each other, which is referred to as channelaggregation.

In FIG. 5, only the first three types of channels are used. The whole160 MHz frequency band (from 5170 MHz to 5330 MHz) is divided into eight20 MHz sub-bands or channels as shown in subfigure 510. Subfigure 520illustrates the P20, S20 and S40 channels allocated for each AP. Notethat even though the three channels of each AP do not overlap with eachother, an AP's channel may overlap with a channel of a different AP asthese APs share the same frequency. It is assumed that these three APsbroadcast their channel configurations. The wireless device may receiveand decode the configurations, and then calculate the priority for eachsub-band, and hence for each consolidated set of sub-bands, using belowmethods. Table 530 defines different weights for each channel type. Ifsub-band A is assigned as a P20 channel for an AP, then sub-band A getsweight 1 for the AP. If sub-band B is assigned as a S20 channel for anAP, then sub-band B gets weight 2 for the AP. If sub-bands C and D areassigned as a S40 channel for an AP, then the weights sub-bands C and Dget for the AP are both 4. If sub-band E is not selected by an AP as anytype of channel, then sub-band E gets weight 8 for the AP. The first rowof table 540 denotes the sub-band indices. Rows 2-4 of table 540correspond to the weights each sub-band gets for the three coexistingAps. Each column of table 540 corresponds to a sub-band. The priority ofa sub-band is calculated by adding together the weights this sub-bandgets from all APs. The last row of table 540 provides the calculatedpriorities.

The method 400 proceeds to step 430, where the wireless devicedetermines one or more CCA statuses for one or more sub-bands in theplurality of sub-bands in accordance with the priorities for theplurality of sub-bands. Sometimes the wireless device has a small amountof data to send so the transmission only requires part of the sharedspectrum. In this case, the CCA status for each of the sub-bands may bedetermined sequentially in a descending order of the priorities of thesub-bands. Hence, sub-bands that are more likely to have an idle CCAstatus are measured and selected first. Once the wireless device selectsenough idle sub-bands for the data transmission, it may stop performingadditional CCA status measurements on the rest of sub-bands, whichimproves the efficiency. In the example of FIG. 5, the wireless devicemay first start the CCA status measurement on sub-band 64 which has thehighest priority 24. Then the wireless device may choose sub-band 44(with priority 20), and sub-bands 60 (with priority 17), and so on andso forth till enough sub-bands are selected. In another embodiment, thewireless device may abandon some low priority sub-bands in thebeginning, and only perform CCA status measurements on some selectedsub-bands with higher priorities. In the example of FIG. 5, the wirelessdevice may ignore the sub-bands with priorities lower than 20 and onlyperform CCA status measurements on sub-bands 64 and 44.

In another embodiment, the wireless device may consolidate a set ofsub-bands. The priority of a consolidated sub-band can be calculated asthe sum of the priorities of each separate sub-band in the set. The 160MHz frequency band in FIG. 5 can be divided into four 40 MHz sub-bandsor two 80 MHz sub-bands, as illustrated by subfigures 550 and 560,respectively. A 40 MHz sub-band is obtained by consolidating twoadjacent 20 MHz sub-bands, and an 80 MHz sub-band is obtained byconsolidating four adjacent 20 MHz sub-bands. The priorities for eachsub-band configuration are provided on the bottom of subfigures 550 and560, respectively.

In another embodiment, the priority may be combined with the CCAbandwidth adjustment method illustrated in FIG. 3. If the CCA bandwidthadjustment condition for dividing sub-bands is detected, the wirelessdevice may first divide a wider sub-band into a set of narrowersub-bands. Then the wireless device may determine how to perform CCA onthe set of narrower sub-bands in accordance with the priorities of thesenarrower sub-bands. For example, the wireless device obtains a busy CCAstatus on an 80 MHz sub-band (e.g., sub-band 1 in subfigure 560). Thenthe wireless device may decide to transmit data on a narrower sub-bandin order to avoid a potential interference. The wireless device maydivide the 80 MHz sub-band into two 40 MHz sub-bands (e.g., sub-bands 3and 4 in subfigure 550), and choose one for data transmission. Insteadof performing CCA status measurements on both 40 MHz sub-bands, and thenselecting one sub-band with an idle CCA status, the wireless device mayjust directly perform CCA status measurement on the 40 MHz sub-band withthe highest priority (e.g., sub-band 4 with priority 36). This is moreefficient because the sub-band with a higher priority is less likely tobe occupied. If the CCA status on the sub-band with the highest priorityis still busy, the wireless device may perform CCA on the sub-band withthe second highest priority.

Although in this disclosure some embodiments are described in thecontext of a UE obtaining uplink channel access, it should beappreciated that such embodiments are not so limited and are equallyapplicable to downlink channel access in a perspective of a basestation, and vice versa.

FIG. 6 illustrates a block diagram of an embodiment processing system600 for performing methods described herein, which may be installed in ahost device. As shown, the processing system 600 includes a processor604, a memory 606, and interfaces 610-614, which may (or may not) bearranged as shown in FIG. 6. The processor 604 may be any component orcollection of components adapted to perform computations and/or otherprocessing related tasks, and the memory 606 may be any component orcollection of components adapted to store programming and/orinstructions for execution by the processor 604. In an embodiment, thememory 606 includes a non-transitory computer readable medium. Theinterfaces 610, 612, and 614 may be any component or collection ofcomponents that allow the processing system 600 to communicate withother devices/components and/or a user. For example, one or more of theinterfaces 610, 612, and 614 may be adapted to communicate data,control, or management messages from the processor 604 to applicationsinstalled on the host device and/or a remote device. As another example,one or more of the interfaces 610, 612, 614 may be adapted to allow auser or user device (e.g., personal computer (PC), etc.) tointeract/communicate with the processing system 600. The processingsystem 600 may include additional components not depicted in FIG. 6,such as long term storage (e.g., non-volatile memory, etc.).

In some embodiments, the processing system 600 is included in a networkdevice that is accessing, or part otherwise of, a telecommunicationsnetwork. In one example, the processing system 600 is in a network-sidedevice in a wireless or wireline telecommunications network, such as abase station, a relay station, a scheduler, a controller, a gateway, arouter, an applications server, or any other device in thetelecommunications network. In other embodiments, the processing system600 is in a user-side device accessing a wireless or wirelinetelecommunications network, such as a mobile station, a UE, a PC, atablet, a wearable communications device (e.g., a smartwatch, etc.), orany other device adapted to access a telecommunications network.

In some embodiments, one or more of the interfaces 610, 612, 614connects the processing system 600 to a transceiver adapted to transmitand receive signaling over the telecommunications network. FIG. 7illustrates a block diagram of a transceiver 700 adapted to transmit andreceive signaling over a telecommunications network. The transceiver 700may be installed in a host device. As shown, the transceiver 700comprises a network-side interface 702, a coupler 704, a transmitter706, a receiver 708, a signal processor 710, and a device-side interface712. The network-side interface 702 may include any component orcollection of components adapted to transmit or receive signaling over awireless or wireline telecommunications network. The coupler 704 mayinclude any component or collection of components adapted to facilitatebi-directional communication over the network-side interface 702. Thetransmitter 706 may include any component or collection of components(e.g., up-converter, power amplifier, etc.) adapted to convert abaseband signal into a modulated carrier signal suitable fortransmission over the network-side interface 702. The receiver 708 mayinclude any component or collection of components (e.g., down-converter,low noise amplifier, etc.) adapted to convert a carrier signal receivedover the network-side interface 702 into a baseband signal. The signalprocessor 710 may include any component or collection of componentsadapted to convert a baseband signal into a data signal suitable forcommunication over the device-side interface(s) 712, or vice-versa. Thedevice-side interface(s) 712 may include any component or collection ofcomponents adapted to communicate data-signals between the signalprocessor 710 and components within the host device (e.g., theprocessing system 600, local area network (LAN) ports, etc.).

The transceiver 700 may transmit and receive signaling over any type ofcommunications medium. In some embodiments, the transceiver 700transmits and receives signaling over a wireless medium. For example,the transceiver 700 may be a wireless transceiver adapted to communicatein accordance with a wireless telecommunications protocol, such as acellular protocol (e.g., LTE, etc.), a wireless local area network(WLAN) protocol (e.g., Wi-Fi, etc.), or any other type of wirelessprotocol (e.g., Bluetooth, near field communication (NFC), etc.). Insuch embodiments, the network-side interface 702 comprises one or moreantenna/radiating elements. For example, the network-side interface 702may include a single antenna, multiple separate antennas, or amulti-antenna array configured for multi-layer communication, e.g.,single input multiple output (SIMO), multiple input single output(MISO), multiple input multiple output (MIMO), etc. In otherembodiments, the transceiver 600 transmits and receives signaling over awireline medium, e.g., twisted-pair cable, coaxial cable, optical fiber,etc. Specific processing systems and/or transceivers may utilize all ofthe components shown, or only a subset of the components, and levels ofintegration may vary from device to device.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods might beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

What is claimed is:
 1. A method for channel access in a wirelesscommunication system, the method comprising: determining, by a wirelessdevice, at least a single Clear Channel Assessment (CCA) status for atleast a single sub-band during a first period; detecting, by thewireless device, a CCA bandwidth adjustment condition for dividing thesingle sub-band into two or more separate sub-bands, wherein acombination of the two or more separate sub-bands occupies the samefrequency band as the single sub-band; and determining, by the wirelessdevice, a separate CCA status for each of the two or more separatesub-bands during a second period.
 2. The method of claim 1, wherein thesingle sub-band belongs to a set of aggregated sub-bands.
 3. The methodof claim 2, wherein determining at least the single CCA status for atleast the single sub-band during the first period comprises: determiningCCA statuses for other sub-bands in the set of aggregated sub-bandsduring the first period.
 4. The method of claim 3, wherein the CCAbandwidth adjustment condition is detected when a number of sub-bands,in the set of aggregated sub-bands, having an idle CCA status is lessthan a threshold number of sub-bands.
 5. The method of claim 3, whereinthe CCA bandwidth adjustment condition is detected when an error rate ofone or more data transmissions of the wireless device over one or moresub-bands in the set of sub-bands exceeds a threshold error rate, theone or more data transmissions occurring prior to the second period. 6.The method of claim 5, wherein the error rate is determined by afeedback from a receiver, the feedback from the receiver comprising ahybrid automatic repeat request (HARQ) acknowledged (ACK), an HARQnot-acknowledged (NACK), an HARQ discontinuous transmission (DTX), or animplicit decoding success indication in up-link (UL) grant downlinkcontrol information (DCI).
 7. The method of claim 3, wherein the CCAbandwidth adjustment condition is detected when both (i) an error rateof one or more data transmissions of the wireless device over one ormore sub-bands exceeds a threshold error rate and (ii) a number ofsub-bands in the set of aggregated sub-bands having an idle CCA statusis less than a threshold number of sub-bands.
 8. The method of claim 3,wherein the CCA bandwidth adjustment condition is detected when allsub-bands in the set of aggregated sub-bands maintain a busy CCA statusfor at least a threshold number of periods.
 9. The method of claim 1,wherein upon detecting the CCA bandwidth adjustment condition, abandwidth of each of the two or more separate sub-bands, for which theseparate CCA statuses are determined during the second period, is equalto the minimum operation bandwidth used by a set of coexisting wirelesssystems during the first period.
 10. The method of claim 1, wherein upondetecting the CCA bandwidth adjustment condition, a bandwidth of each ofthe two or more separate sub-bands, for which the separate CCA statusesare determined during the second period, is equal to an operationbandwidth used by more than a threshold number of coexisting wirelesssystems in a set of coexisting wireless systems during the first period.11. A wireless device comprising: a processor; and a non-transitorycomputer readable storage medium storing programming for execution bythe processor, the programming including instructions to: determine atleast a single Clear Channel Assessment (CCA) status for at least asingle sub-band during a first period; detect a CCA bandwidth adjustmentcondition for dividing the single sub-band into two or more separatesub-bands, wherein a combination of the two or more separate sub-bandsoccupies the same frequency band as the single sub-band; and determine aseparate CCA status for each of the two or more separate sub-bandsduring a second period.
 12. The method of claim 4, wherein the idle CCAstatus on a sub-band is determined if an energy level of noise andinterference on the sub-band is smaller than a threshold level.
 13. Themethod of claim 8, wherein the busy CCA status on a sub-band isdetermined if an energy level of noise and interference on the sub-bandexceeds a threshold level.
 14. The method of claim 2, wherein the set ofaggregated sub-bands occupies a continuous frequency band.
 15. Themethod of claim 2, wherein at least two sub-bands in the set ofaggregated sub-bands are separated by a gap in frequency domain, andwherein the gap is not occupied by the set of aggregated sub-bands. 16.The method of claim 5, wherein the single CCA status and the error rateare both determined during one or more sub-frames in a Maximum ChannelOccupancy Time (MCOT).
 17. The method of claim 5, wherein the single CCAstatus is determined during one or more sub-frames in a Maximum ChannelOccupancy Time (MCOT), and the error rate is determined during the MCOT.18. The method of claim 3, further comprising: receiving beacons and/orpreambles transmitted from different coexisting wireless systems; andcalculating priorities for each sub-band in the set of aggregatedsub-bands in accordance with channel configuration information in thebeacons and/or the preambles received from the different coexistingwireless systems, wherein sub-bands having higher priorities are lesslikely to be occupied by a data transmission of the different coexistingwireless systems than sub-bands having lower priorities.
 19. The methodof claim 18, wherein determining CCA statuses for the single sub-bandand the other sub-bands in the set of aggregated sub-bands comprisesdetermining CCA statuses for the single sub-band and the other sub-bandsin the set of aggregated sub-bands in accordance with the priorities foreach sub-band in the set of aggregated sub-bands.
 20. The wirelessdevice of claim 11, wherein the single sub-band belongs to a set ofaggregated sub-bands.
 21. The wireless device of claim 20, whereininstructions to determine at least the single CCA status for at leastthe single sub-band during the first period comprise instructions todetermine CCA statuses for other sub-bands in the set of aggregatedsub-bands during the first period.
 22. The wireless device of claim 21,wherein the CCA bandwidth adjustment condition is detected when a numberof sub-bands, in the set of aggregated sub-bands, having an idle CCAstatus is less than a threshold number of sub-bands.
 23. The wirelessdevice of claim 21, wherein the CCA bandwidth adjustment condition isdetected when an error rate of one or more data transmissions of thewireless device over one or more sub-bands in the set of sub-bandsexceeds a threshold error rate, the one or more data transmissionsoccurring prior to the second period.
 24. The wireless device of claim23, wherein the error rate is determined by a feedback from a receiver,the feedback from the receiver comprising a hybrid automatic repeatrequest (HARQ) acknowledged (ACK), an HARQ not-acknowledged (NACK), anHARQ discontinuous transmission (DTX), or an implicit decoding successindication in up-link (UL) grant downlink control information (DCI).